Several types of spacers for flat panel displays, such as field emission displays, are known in the art. A field emission display includes an envelope structure having an evacuated interspace region between two display plates. Electrons travel across the interspace from a cathode plate (also known as a cathode or a back plate), upon which electron emitting structures, such as Spindt tip or carbon nanotubes, are fabricated, on an anode plate (also known as an anode or face plate), which includes deposits of light emitting materials, or “phosphors”. Typically, the pressure within the evacuated interspace region between the cathode and anode is on the order of 10−6 Torr.
The cathode and anode plates are thin in order to provide low display weight. If the display area is small, such as in a 1 inch diagonal display, and a typical sheet of glass having a thickness of 0.04 inch is utilized for the plates, the display will not collapse or bow significantly. However, if a larger display area is desired, the thin plates are not sufficient to withstand the pressure differential in order to prevent collapse of bowing upon evacuation of the interspace region. For example, a screen having a 30 inch diagonal will have several tons of atmospheric pressure exerted upon it. As a result of this tremendous pressure, spacers play an essential role in large area, light weight displays. Spacers are structures placed between the anode and cathode plates for keeping them a constant distance apart. The spacers, in conjunction with the thin, light weight plates, counteract the atmospheric pressure, allowing the display area to be increased with little or no increase in plate thickness.
Several schemes have been proposed for providing spacers. Some of these schemes include the affixing of spacer (structural members such as glass rods) to the inner surface of one of the display plates. In one such prior art scheme, glass rods are affixed to one of the display plates by applying devitrifying solder glass frit to one end of the rod or post and bonding the frit to the inner surface of one of the display plates. Another known method uses thermocompression bonding to smash one layer of metal into another layer of metal. The bond that is created is strong enough to permit handling and sealing of the device components.
Regardless of the manufacturing process used, the process is inherently vacuum incompatible. Dimensioning, cleaning, and placing of spacers are accomplished in air (out of vacuum). As spacers sit in ambient air, they absorb moisture and hydrocarbons from the atmosphere. Known preventative methods include the use of nitrogen hood or high temperature bake out; however, since many spacers are usually required (as many as 1000 spacers for a 42 inch display, for example), the possibility of having a few contaminated spacers is high. If a spacer is contaminated with water or hydrocarbons and the anode and cathode plates are sealed, the spacers will be visible during normal operation of the display, even with previously known discharging methods.
Accordingly, it is desirable to provide a method for in situ cleaning of spacers separating an anode and cathode of a flat panel display. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.